Adenoviruses are eukaryotic DNA viruses that can be modified to efficiently deliver a therapeutic or reporter transgene to a variety of cell types [see, e.g., M. S. Horwitz et al, "Adenoviridae and Their Replication", Virology, second edition, pp. 1712, ed. B. N. Fields et al, Raven Press Ltd., New York (1990)]. Recombinant adenovirus (rAds) are capable of providing extremely high levels of transgene delivery to virtually all cell types, regardless of the mitotic state. The efficacy of this system in delivering a therapeutic transgene in vivo that complements a genetic imbalance has been demonstrated in animal models of various disorders [K. F. Kozarsky et al, Somatic Cell Mol. Genet., 19:449-458 (1993) ("Kozarsky et al I"); K. F. Kozarsky et al, J. Biol. Chem., 269:13695-13702 (1994) ("Kozarsky et al II) and others]. The use of recombinant adenoviruses in the transduction of genes into hepatocytes in vivo has previously been demonstrated in rodents and rabbits [see, e.g., Kozarsky II, cited above, and S. Ishibashi et al, J. Clin. Invest., 92:883-893 (1993)].
The first-generation recombinant, replication-deficient adenoviruses which have been developed for gene therapy contain deletions of the entire E1a and part of the E1b regions. This replication-defective virus is grown on an adenovirus-transformed, complementation human embryonic kidney cell line containing a functional adenovirus E1a gene which provides a transacting E1a protein, the 293 cell [ATCC CRL1573]. E1-deleted viruses are capable of replicating and producing infectious virus in the 293 cells, which provide E1a and E1b region gene products in trans. The resulting virus is capable of infecting many cell types and can express the introduced gene (providing it carries its own promoter), but cannot replicate in a cell that does not carry the E1 region DNA unless the cell is infected at a very high multiplicity of infection.
Adeno-associated virus (AAV) is an integrating human DNA parvovirus which has been proposed for use as a gene delivery vehicle for somatic gene therapy [B. J. Carter, in "Handbook of Parvoviruses", ed., P. Tijsser, CRC Press, pp.155-168 (1990)]. This small non-enveloped virus contains a 4.6 kb single stranded (ss) DNA genome that encodes sets of regulatory and capsid genes called rep and cap. Rep polypeptides (rep78, rep68, rep62 and rep40) are involved in replication, rescue and integration of the AAV genome. The cap proteins (VP1, VP2 and VP3) form the virion capsid. Flanking the rep and cap open reading frames at the 5' and 3' ends are 145 bp inverted terminal repeats (ITRs), the first 125 bp of which are capable of forming Y- or T-shaped duplex structures.
Recombinant forms of AAV (rAAV) have been developed as vectors by replacing all viral open reading frames with a therapeutic minigene, while retaining the necessary cis elements contained in the ITRs. [See, e.g., U.S. Pat. Nos. 4,797,368; 5,153,414; 5,139,941; 5,252,479; and 5,354,678; and International Publication Nos. WO 91/18088 published Nov. 28, 1991; WO 93/24641 published Dec. 9, 1993 and WO94/13788 published Jun. 23, 1994]. However, progress towards establishing AAV as a transducing vehicle for gene therapy has been slow for a variety of reasons. For example, the integrated provirus preferentially targets specific sites in chromosome 19. Additionally, difficulties surround large-scale production of replication defective recombinants. The cells employed to produce rAAV must also be infected with adenovirus or herpesvirus to provide the necessary helper functions, thereby producing problems in purifying recombinant AAV (rAAV) from contaminating virus in culture. Practical experience with purified recombinant AAV as a gene therapy vector has been disappointing, because the more purified the AAV is from co-infection with its helper virus in culture, the lower the gene transduction efficiencies that the rAAV displays.
There remains a need in the art for additional recombinant adenoviruses and rAAV, therapeutic compositions and methods which enable effective use of these recombinant viruses in the treatment of disorders and diseases by gene therapy.